1. Field of the Invention
The present invention relates to a sheet ejecting device.
2. Description of Related Art
Typically, an image forming apparatus including a post-processing device such as a printer, copier, etc. is provided with a placement stage to temporarily stock a plurality of sheets on which images are formed in the apparatus and a sheet placement stage such as a sheet ejection tray to stock sheets ejected outside the apparatus.
Conventionally, when a sheet is ejected to such sheet placement stage, there is a problem that the stacking position is misaligned anywhere between from when the sheet separates from the sheet conveying roller directly before the sheet placement stage to when the sheet drops by its own weight onto the sheet placement stage and is stacked, and the sheets are not stacked on the sheet placement stage in a state where the edges of the sheets are aligned.
This problem occurs regardless of whether the placement face of the sheet placement stage is a horizontal configuration or is a tilted configuration. The problem especially occurs when the sheet conveying speed is high or when the environmental conditions are severe such as high temperature and high humidity or low temperature and low humidity.
In view of the above, there is disclosed a technique where sheets are stacked in a stacker, an edge of the stacked sheets is gripped with a gripper, and the gripper is moved to stack the sheets on the sheet ejection tray (for example, Japanese Patent Application Laid-Open Publication No. 2008-273656).
When a sheet which slips such as a coated sheet, thick sheet, etc., is gripped with the gripper, or when two overlapped normal sheets are gripped with the gripper, there is a possibility that the sheets slip even when gripped with the gripper and the sheets are not properly stacked on the sheet ejection tray. Specifically, this can be seen clearly in a high speed machine. In order to avoid the above problems, it is possible to consider increasing the gripping force of the gripper. However, this results in creases, folds, etc. easily forming on the sheets which is not a preferable state.